TEMPERATURE AND LIFE. 409 



liberation of matter from the lire, consequently there must be likewise a 

 liberation of matter from the combustion in the lungs." That is to say, 

 since the lungs evolve carbonic acid, a generation of heat must follow,for 

 the reason that heat is under all circumstances an accompaniment of 

 combustion. A living organism produces heat because it burns. The 

 study of a century goes to show the accuracy of this conclusinn. 



According to Lavoisier the lungs appear to be the seat of respiratory 

 combustion and calorification. On this point however he is guarded 

 in what he says, and this reserve is justifiable, as, in point of fact, their 

 role is quite a different one from that which he supposes. Lagrange, 

 a short time after Lavoisier, combatted this supposition, stating that 

 if the lungs were actually the seat of these combustions, the heat gen- 

 erated would be of such intensity that this organ would sutier injury 

 sufficiently serious to be incompatible with life. This, however, is an 

 exaggeration. The production of heat has been estimated, and, even 

 supposing tlie lungs to be the exclusive seat of this function, the tem- 

 l)erature of this organ would not be intense enough to be injurious. 

 The most exact researches have shown what is the work assigned to 

 the lungs in the process of calorification. This organ which, owing to 

 its innumerable cells, representing a surface of 150 or 200 square 

 metres (this, although astonishing, is indisputable), onl}'^ serves to bring 

 in contact the blood and the air. The net-work of capillaries, separated 

 from the air by a fine layer of cells, represents a surface equal to about 

 three-fourths of that of the entire lungs, and forms a sanguineous coat- 

 ing of 100 or 150 square metres. This has little depth, it is true, only 

 containing 2 litres of blood. This however signifies little, for in order 

 to secure absorption, it is extent of surface rather than dejith which is 

 required; the latter being of slight consequence. Moreover if there 

 are at a given moment 2 litres of blood in the lungs it is estimated by 

 a simple calculation that the total quantity of blood passing through 

 the lungs in the course of 24 hours is about 20,000 litres. In fact, the 

 anatomy of the lungs is admirably arranged to give them this absorb- 

 ing capacity, and experience shows that their role is exactly that for 

 which their organization is best adapted. The blood which permeates 

 the lungs absorbs the oxjgen in the inhaled air, by reason of a chemical 

 affinity between the hfemoglobine of these red globules and that gas, 

 and carries it throughout the body. It is in the recesses of the tissues 

 over all parts of the organism that this oxygen, separating itself from 

 the hsemoglobine, unites with the carbon of the tissues, and ignites in 

 order to give birth to heat and carbonic acid; necessary results of all 

 combustion. The acid which is taken up by the blood is finally expelled 

 tlirough the lungs. 



Calorification is thus the result of combustions which take place at 

 all points of the animal economy. It is in complete dependence upon 

 the relations of two other functions — respiration (that is (o say, the sup- 

 ply of oxygen for burning) and alimentation (the supply of carbon or of 



